Semiconductor integrated circuit device and manufacturing method of semiconductor integrated circuit device

ABSTRACT

After formation of Cu interconnections  46   a  to  46   e  each to be embedded in an interconnection groove  40  of a silicon oxide film  39  by CMP and then washing, the surface of each of the silicon oxide film  39  and Cu interconnections  46   a  to  46   e  is treated with a reducing plasma (ammonia plasma). Then, without vacuum break, a cap film (silicon nitride film) is formed continuously. This process makes it possible to improve the dielectric breakdown resistance (reliability) of a copper interconnection formed by the damascene method.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a semiconductor integrated circuitdevice and a manufacturing method thereof, in particular, a techniqueeffective when adapted for the so-called damascene method wherein aninterconnection having copper as a main conductive layer is formed bycutting a groove in an insulating film, forming a copper film to beembedded in the groove and polishing by CMP (Chemical MechanicalPolishing).

[0002] Attendant on the recent tendency to miniaturizing aninterconnection in a semiconductor integrated circuit device, adeterioration in the performance of the semiconductor integrated circuitdevice resulting from an increase in interconnection resistance orinterconnection delay has come to be a problem. It has led to a seriousproblem particularly in a high-performance logic LSI as a factor fordisturbing its performance. As described on pages 15 to 21 in thePreprint of 1993 VMIC (VLSI Multilevel Interconnection Conference), amethod for forming an interconnection pattern in an interconnectiongroove by embedding a metal, which has copper (Cu) as a main conductivelayer, in an interconnection groove formed in an insulating film andthen removing the unnecessary portion of the metal outside theinterconnection groove by chemical mechanical polishing (CMP) is nowunder investigation.

[0003] Described in Japanese Patent Application Laid-Open No. Hei9-306915 is a technique which comprises forming an interconnectiongroove in a silicon oxide film on a semiconductor substrate, depositinga titanium nitride film and copper film by sputtering, filling thegroove with copper by reflow, removing the copper film outside thegroove by CMP and then heat treating in a hydrogen atmosphere. Accordingto it, defects in the copper interconnection can be reduced by thistechnique.

[0004] Described in Japanese Patent Application Laid-Open No. Hei10-56014 is a technique comprising polishing a material, which has atitanium nitride film and tungsten film and is formed over asemiconductor substrate, by CMP and subjecting the polished surface toplasma treatment with a halogen-based mixed gas. According to it, nointerconnection short-circuit occurs even if micro scratches are formedby CMP.

[0005] Described in Japanese Patent Application Laid-Open No. Hei10-56014 is a technique comprising forming a photosensitive SOG filmover a base on which an interconnection is to be formed, forming aninterconnection groove in the SOG film, forming a titanium nitride film,a copper film and a copper titanium alloy film, leaving the films onlyinside of the interconnection groove by CMP, and heat treating in anammonia atmosphere to form a titanium nitride film over the surfacelayer of the copper titanium alloy film.

[0006] Described in Japanese Patent Application Laid-Open No. Hei11-16912 is a technique of subjecting the surface of a through-hole orthe like of a copper interconnection formed by the damascene method toplasma treatment in an atmosphere such as ammonia.

SUMMARY OF THE INVENTION

[0007] The present inventors have found the below-described problems inthe interconnection forming technique, so called damascene method, whichcomprises forming the above-described interconnection groove, forming ametal film (ex. copper film) to be embedded in the groove and removingthe copper film outside the interconnection groove by CMP.

[0008] When application of the above-described technique tohigh-performance logic LSI is considered, a reduction in interconnectionresistance is one of the most important problems to be technicallyinvestigated. The present inventors therefore are now investigatingcopper as a metal constituting the interconnection. Copper tends to bediffused in a silicon oxide film, which is an insulating film, comparedwith another metal (ex. aluminum or tungsten) so that a barrier filmcovering the interconnection must be studied. As the barrier film in theinterconnection groove, a titanium nitride film is studied. As a film(cap film) covering the upper portion of the interconnection, a siliconnitride film is studied. Reliability improvement of the interconnectionby covering copper with the titanium nitride film lying on theinterconnection groove and the silicon nitride film for capping theupper portion of the interconnection, thereby blocking diffusion ofcopper into the intrastratum insulating film (silicon oxide film) isunder investigation.

[0009] When copper is employed as an interconnection material, TDDB(Time Dependence on Dielectric Breakdown) is markedly short comparedwith another metal material (ex. aluminum or tungsten). The TDDB test isone of acceleration test methods for evaluating the dielectric breakdownresistance between interconnections. According to it, time dependence ondielectric breakdown (lifetime) under the ordinary using condition canbe estimated from the time dependence on dielectric breakdown under ahigher electric field at a higher predetermined temperature than theordinary using condition. The TDDB is a lifetime estimated from thisTDDB test. The TDDB will be described later in detail.

[0010]FIG. 55 is a graph illustrating the measured data of TDDBcharacteristics of a copper interconnection, an aluminum interconnectionand a tungsten interconnection. The TDDB and electric field strength areplotted along the ordinate and abscissa, respectively. When thecharacteristics (data A) of the aluminum interconnection and those (dataB) of the tungsten interconnection are extrapolated, the TDDB at anelectric field strength of 0.2 MV/cm (ordinary using condition) easilyexceeds 3×10⁸ sec (10 years), which is a development target of thepresent inventors. When the characteristics (data C) of the copperinterconnection is extrapolated, on the other hand, there is almost nomargin for the development target of 10 years. The aluminuminterconnection is formed by film deposition and patterning byphotolithography, while the tungsten interconnection is formed by thedamascene method similar to the copper interconnection. The copperinterconnection and tungsten interconnection differ only in thematerial. There is no difference in their structures. A markeddifference in TDDB characteristics between these two materials suggeststhat it results from the difference in the interconnection material.Here, the TDDB characteristics are measured at 140° C.

[0011] A deterioration in the TDDB characteristics is generally presumedto result from a reduction in the withstand voltage betweeninterconnections due to diffusion of copper, used as an interconnectionmaterial, into its surroundings. According to the investigation by thepresent inventors, however, it is mainly caused by drifting anddiffusion of not copper atoms but ionized copper fed from copper oxideor copper silicide at an electric potential between interconnections.Copper is presumed to be mainly diffused from the interface between aninsulating film having a copper interconnection formed thereon and a capfilm. Described specifically, copper ions are formed from a coppercompound such as copper oxide or copper silicide formed over the surfaceof the copper interconnection and then, such ionized copper drifts andis diffused along the interface between the insulating film wherein aninterconnection is to be formed and a cap film by an electric fieldbetween interconnections. The copper atoms thus diffused are presumed toincrease a leak current. The increase in the leak current heightensthermal stress and finally causes dielectric breakdown at a leak path,leading to the expiration of the lifetime. This mechanism will bedescribed later in detail.

[0012] According to the investigation by the present inventors,formation of a multilayered interconnection layer causes a problem thatthere appears peeling between the lower interconnection and insulatingfilm (cap film) formed thereover in the CMP step for forming an upperinterconnection.

[0013] In addition, use of a silicon nitride film as a cap film on thecopper interconnection is accompanied with the problem that a silicideis formed on the interface between copper and a silicon nitride film,causing an increase in the resistance of the copper interconnection.

[0014] An object of the present invention is to improve the dielectricbreakdown resistance (reliability) of a copper interconnection formed bythe damascene method.

[0015] Another object of the present invention is to suppress thegeneration of peeling of a cap film from an interconnection layer.

[0016] A further object of the present invention is to prevent anincrease in the resistance of a copper interconnection when a siliconnitride film is employed as a cap film.

[0017] The above-described and the other objects and novel features ofthe present invention will be apparent from the description herein andaccompanying drawings.

[0018] Among the inventions disclosed herein, representative ones willnext be summarized simply.

[0019] In the present invention, the surface of each of aninterconnection and an intrastratum insulating film (ex. silicon oxidefilm) in which the interconnection has been embedded is subjected to areducing plasma after the CMP step but prior to the formation of a capfilm (ex. silicon nitride film).

[0020] This treatment makes it possible to continuously form theinterface between the interconnection and intrastratum insulating film,and the cap insulating film, leading to an improvement in the adhesionon the interface and, in turn, a marked improvement in the TDDBcharacteristics.

[0021] The summaries of the present invention will next be described.

[0022] In one aspect, the present invention provides a manufacturingmethod which comprises forming a first insulating film (ex. siliconoxide film) over a semiconductor substrate; forming a groove(interconnection groove) in the first insulating film; successivelyforming a first conductive film (a blocking film, for example, atitanium nitride film, for preventing diffusion of copper) and a secondconductive film (copper film) to be embedded in the groove; polishingthe second conductive film and first conductive film to form aninterconnection in the groove; treating the surface of each of the firstinsulating film and interconnection to a plasma of reducing atmosphere;and then depositing a first insulating film and, over theinterconnection, a second insulating film (a cap insulating film, forexample, a silicon nitride film).

[0023] In the above-described method, as the plasma of reducingatmosphere, an ammonia (NH₃) plasma or a hydrogen (H₂) plasma can beemployed. In addition, a mixed gas plasma of ammonia (NH₃) and adiluting gas (one or more gases selected from hydrogen (H₂), nitrogen(N₂), argon (Ar) and helium (He)) or a mixed gas plasma of hydrogen (H₂)and a diluting gas (one or more gases selected from ammonia (NH₃),nitrogen (N₂), argon (Ar) and helium (He)) can also be used. The mixedgas contains ammonia or hydrogen in an amount of at least 5%.

[0024] It is possible to form a silicon oxide film as the firstinsulating film, a copper film as the second conductive film and asilicon nitride film as the second insulating film. It is needless tosay that copper may contain alloy elements, additives and/or impuritieswithin an extent not impairing the properties of copper as aninterconnection. In the embodiment, copper having a purity as high as4N, that is, 99.99% or higher is usually employed.

[0025] After the polishing step but prior to plasma treatment, thesurface of each of the first insulating film and interconnection can bewashed with an acid. For washing, an aqueous solution of hydrogenfluoride (HF) or citric acid (C(CH₂COOH)₂(OH)(COOH)) can be employed.

[0026] In the polishing step, abrasive-grain-free chemical mechanicalpolishing can be adopted. Polishing can be conducted in three stages,that is, first polishing by abrasive-grain-free chemical mechanicalpolishing, second polishing by abrasive-grain-using chemical mechanicalpolishing, and third polishing by selective chemical mechanicalpolishing conducted at a 5:1 selection ratio of the first conductivefilm to the second conductive film.

[0027] In another aspect, the present invention provides a manufacturingmethod which comprises forming a first insulating film over asemiconductor substrate, forming a groove in the first insulating film,forming a first conductive film and a second conductive film to embedthe groove therewith, polishing the second and first conductive films toform an interconnection in the groove, subjecting the surface of each ofthe first insulating film and interconnection to reducing treatment andnitriding treatment with a plasma, and then depositing a secondinsulating film over the first insulating film and interconnection.

[0028] In this case, an ammonia (NH₃) plasma, or a mixed gas plasma ofammonia with one or more gases selected from hydrogen (H₂), nitrogen(N₂), argon (Ar) and helium (He) can be used as the plasma.

[0029] In a further aspect, the present invention provides amanufacturing method which comprises forming a first insulating filmhaving a dielectric constant lower than that of a silicon oxide filmcontained in a protecting film (passivation film), forming a groove oropening in the first insulating film, treating the exposed surface ofthe first insulating film with a plasma of reducing atmosphere,depositing a first conductive film which covers the surface includingthe inside wall of the groove or opening, forming a second conductivefilm to be embedded in the groove or opening, and removing the secondconductive film and first conductive film outside the groove or openingby polishing, thereby forming a conductive member in the groove oropening. For this method, the above-described plasma of reducingatmosphere can be used. The second insulating film may be formed overthe first insulating film.

[0030] In a still further aspect, the present invention provides asemiconductor integrated circuit device which comprises a firstinsulating film, an interconnection embedded in the groove of the firstinsulating film, and a second insulating film formed over the firstinsulating film and interconnection, wherein a nitride film is formed onthe interface between the first insulating film and interconnection, andsecond insulating film. In this device, the first insulating film,interconnection and second insulating film are a silicon oxide film,copper and a silicon nitride film, respectively. The nitrogenconcentration in the nitride film becomes higher from the side of thefirst insulating film and interconnection toward the second insulatingfilm.

[0031] In a still further aspect, the present invention provides amanufacturing method which comprises forming a first insulating filmover a semiconductor substrate, forming a groove in the first insulatingfilm, depositing a first conductive film over the first insulating film,forming a second conductive film to embed the groove therewith,polishing the second conductive film and first conductive film to forman interconnection in the groove, treating the surface of each of thefirst insulating film and interconnection with a plasma of reducingatmosphere, and continuously depositing a second insulating film overthe first insulating film and interconnection while maintaining apressure-reduced or inactive condition without exposing thesemiconductor substrate to the atmosphere.

[0032] The summary of the other inventions of the present applicationwill next be described briefly in items.

[0033] 1. A manufacturing method of a semiconductor integrated circuitdevice, which comprises:

[0034] (a) forming a first insulating film over a semiconductorsubstrate and forming a groove in the first insulating film,

[0035] (b) depositing a first conductive film over the first insulatingfilm and forming a second conductive film to embed the groove therewith,

[0036] (c) removing the second conductive film and first conductive filmover the first insulating film outside the groove and forming aninterconnection in the groove,

[0037] (d) treating the surface of each of the first insulating film andinterconnection with a plasma of reducing atmosphere, and

[0038] (e) after completion of the plasma treating step, depositing asecond insulating film over the first insulating film andinterconnection.

[0039] 2. A manufacturing method according to the item 1, wherein theplasma of reducing atmosphere is an ammonia (NH₃) plasma or hydrogen(H₂) plasma.

[0040] 3. A manufacturing method according to the item 1, wherein theplasma of reducing atmosphere is mixed gas plasma of ammonia (NH₃) and adiluting gas, and the diluting gas contains one or more gases selectedfrom hydrogen (H₂), nitrogen (N₂), argon (Ar) and helium (He).

[0041] 4. A manufacturing method according to the item 3, wherein theconcentration of ammonia (NH₃) is at least 5 wt. % based on the mixedgas.

[0042] 5. A manufacturing method according to the item 1, wherein theplasma of reducing atmosphere is a mixed gas plasma of hydrogen (H₂) anda diluting gas and the diluting gas contains one or more gases selectedfrom ammonia (NH₃), nitrogen (N₂), argon (Ar) and helium (He).

[0043] 6. A manufacturing method according to the item 5, wherein theconcentration of hydrogen (H₂) is at least 5 wt. % based on the mixedgas.

[0044] 7. A manufacturing method according to the item 1, wherein thefirst insulating film is a silicon oxide film and the second conductivefilm is made of copper.

[0045] 8. A manufacturing method according to the item 7, wherein thesecond insulating film is a silicon nitride film.

[0046] 9. A manufacturing method according to the item 8, wherein theplasma of reduced atmosphere is an ammonia (NH₃) plasma or a hydrogen(H₂) plasma, or a mixed gas plasma thereof with one or more gasesselected from nitrogen (N₂), argon (Ar) and helium (He).

[0047] 10. A manufacturing method according to the item 9, wherein thecopper has a purity as high as 99.99% or greater.

[0048] 11. A manufacturing method according to the item 1, which furthercomprises washing the surface of each of the first insulating film andinterconnection with an acid between the steps (c) and (d).

[0049] 12. A manufacturing method according to the item 11, wherein anaqueous solution of hydrogen fluoride (HF) or citric acid(C(CH₂COOH)₂(OH)(COOH) is used as the acid for washing.

[0050] 13. A manufacturing method according to the item 12, wherein thefirst insulating film, the second conductive film and the secondinsulating film are a silicon oxide film, copper and a silicon nitridefilm, respectively.

[0051] 14. A manufacturing method according to the item 12, wherein theplasma of reduced atmosphere is an ammonia (NH₃) plasma or a hydrogen(H₂) plasma, or a mixed gas plasma thereof with one or more gasesselected from nitrogen (N₂), argon (Ar) and helium (He).

[0052] 15. A manufacturing method according to the item 14, wherein thecopper has a purity as high as 99.99% or greater.

[0053] 16. A manufacturing method according to the item 1, whereinabrasive-grain-free chemical mechanical polishing is employed for thepolishing in the step (c).

[0054] 17. A manufacturing method according to the item 16, wherein thepolishing in the step (c) is conducted in three stages, that is, firstpolishing by abrasive-grain-free chemical mechanical polishing, secondpolishing by abrasive-grain-using chemical mechanical polishing andthird polishing by selective chemical mechanical polishing at a firstconductive film: second conductive film selection ratio of at least 5.

[0055] 18. A manufacturing method according to the item 17, wherein thefirst insulating film, the second conductive film and the secondinsulating film are a silicon oxide film, copper and a silicon nitridefilm, respectively.

[0056] 19. A manufacturing method according to the item 18, wherein theplasma of reduced atmosphere is an ammonia (NH₃) plasma or a hydrogen(H₂) plasma, or a mixed gas plasma thereof with one or more gasesselected from nitrogen (N₂), argon (Ar) and helium (He).

[0057] 20. A manufacturing method according to the item 19, whichfurther comprises, between the steps (c) and (d), washing the surface ofeach of the first insulating film and interconnection with an aqueoussolution of hydrogen fluoride (HF) or citric acid(C(CH₂COOH)₂(OH)(COOH).

[0058] 21. A manufacturing method according to the item 20, wherein thecopper has a purity as high as 99.99% or greater.

[0059] 22. A manufacturing method of a semiconductor integrated circuitdevice, which comprises:

[0060] (a) forming a first insulating film over a semiconductorsubstrate and forming a groove in the first insulating film,

[0061] (b) depositing a first conductive film over the first insulatingfilm and forming a second conductive film to embed the groove therewith,

[0062] (c) removing the second conductive film and first conductive filmover the first insulating film outside the groove by polishing andforming an interconnection in the groove,

[0063] (d) subjecting the surface of each of the first insulating filmand interconnection to reducing treatment and nitriding treatment with aplasma, and

[0064] (e) depositing the second insulating film over the firstinsulating film and interconnection.

[0065] 23. A manufacturing method according to the item 22 wherein theplasma is an ammonia (NH₃) plasma or a mixed gas plasma thereof with adiluting gas, and the diluting gas is at least one gas selected fromhydrogen (H₂), nitrogen (N₂), argon (Ar) and helium (He).

[0066] 24. A manufacturing method of a semiconductor integrated circuithaving a first insulating film formed over a semiconductor substrate anda protecting film formed thereover for preventing the invasion ofimpurities, which comprises:

[0067] (a) forming a first insulating film having a dielectric constantlower than that of a silicon oxide film contained in the protectingfilm,

[0068] (b) forming a groove or opening in the first insulating film,

[0069] (c) treating the exposed surface of the first insulating filmwith a plasma of reducing atmosphere,

[0070] (d) depositing a first conductive film to cover the surfaceincluding the inside wall of the groove or opening and forming a secondconductive film to embed therewith the groove or opening, and

[0071] (e) removing the second conductive film and first conductive filmoutside the groove or opening by polishing and forming a conductivemember in the groove or opening.

[0072] 25. A manufacturing method according to the item 24, wherein theplasma of reduced atmosphere is an ammonia (NH₃) plasma or a hydrogen(H₂) plasma, or a mixed gas plasma thereof with one or more gasesselected from nitrogen (N₂), argon (Ar) and helium (He).

[0073] 26. A manufacturing method according to the item 25, wherein asecond insulating film is formed over the first insulating film, agroove or opening is formed in the first and second insulating films inthe step (b) and the surface of the first insulating film exposed to theinside wall of the groove or opening is treated with a plasma ofreducing atmosphere.

[0074] 27. A semiconductor integrated circuit device having a firstinsulating film formed over a semiconductor substrate, aninterconnection embedded in a groove of the first insulating film and asecond insulating film formed over the first insulating film andinterconnection, wherein a nitride film is formed on the interfacebetween the first insulating film and interconnection, and the secondinsulating film.

[0075] 28. A semiconductor integrated circuit device according to theitem 27, wherein the first insulating film, interconnection and secondinsulating film are a silicon oxide film, copper and silicon nitridefilm, respectively.

[0076] 29. A semiconductor integrated circuit device according to theitem 28, wherein the nitrogen concentration of the nitride film becomeshigher from the first insulating film and interconnection toward thesecond insulating film.

[0077] 30. A manufacturing method according to the item 1, which furthercomprises, after the completion of the step (d), depositing the secondinsulating film over the first insulating film and interconnectioncontinuously while maintaining a reduced-pressure or inactive conditionwithout exposing the semiconductor substrate to the atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

[0078]FIG. 1 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing method of a semiconductorintegrated circuit device according to one embodiment (Embodiment 1) ofthe present invention;

[0079]FIG. 2 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0080]FIG. 3 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0081]FIG. 4 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0082]FIG. 5 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0083]FIG. 6(a) is a plan view illustrating the manufacturing method ofEmbodiment 1 and FIG. 6(b) is a fragmentary cross-sectional viewillustrating the manufacturing method of Embodiment 1;

[0084]FIG. 7(a) is a plan view illustrating the manufacturing method ofEmbodiment 1 and FIG. 7(b) is a fragmentary cross-sectional viewillustrating the manufacturing method of Embodiment 1;

[0085]FIG. 8 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0086]FIG. 9 is a schematic view illustrating one example of the wholeconstitution of a CMP apparatus used for the formation of a Cu-embeddedinterconnection;

[0087]FIG. 10 is a schematic view illustrating a part of the CMPapparatus used for the formation of a Cu-embedded interconnection;

[0088]FIG. 11 is a perspective view illustrating a scrub washing methodof a wafer;

[0089]FIG. 12 is a schematic view illustrating another example of thewhole constitution of a CMP apparatus used for the formation of aCu-embedded interconnection;

[0090]FIG. 13 is a schematic view illustrating a further example of thewhole constitution of a CMP apparatus used for the formation of aCu-embedded interconnection;

[0091]FIG. 14 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0092]FIG. 15(a) is a schematic cross-sectional view of a plasmatreating apparatus used for ammonia plasma treatment an deposition of asilicon nitride film and FIG. 15(b) is a plan view of the apparatus;

[0093]FIG. 16 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0094]FIG. 17 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of Embodiment 1;

[0095]FIG. 18 is a flow chart illustrating the manufacturing method ofthe semiconductor integrated circuit device of Embodiment 1;

[0096]FIG. 19 is a schematic cross-sectional view illustrating thesemiconductor integrated circuit device of Embodiment 1;

[0097]FIG. 20 is a graph illustrating TDDB;

[0098]FIG. 21 is a graph illustrating TDDB;

[0099] FIGS. 22(a) to 22(d) are graphs each illustrating XPS data;

[0100] FIGS. 23(a) to 23(d) are graphs each illustrating XPS data;

[0101] FIGS. 24(a) to 24(d) are graphs each illustrating XPS data;

[0102] FIGS. 25(a) to 25(d) are graphs each illustrating XPS data and(f) is a table showing a component ratio;

[0103] FIGS. 26(a) to 26(d) are graphs each illustrating the results ofmass spectroscopy;

[0104] FIGS. 27(a) to 27(d) are graphs each illustrating the results ofmass spectroscopy;

[0105]FIG. 28 is a TEM photograph of the interconnection portion ofEmbodiment 1;

[0106]FIG. 29 is TEM photograph for comparison;

[0107]FIG. 30 is a graph illustrating interconnection resistance;

[0108]FIG. 31(a) is a TEM photograph of the interconnection portionwithout treatment, FIG. 31(b) is a TEM photograph of the interconnectionportion of Embodiment 1, and FIGS. 31(c) and 31(d) are traced drawingsof FIGS. 31(a) and 31(b), respectively;

[0109] FIGS. 32(a) to 32(c) are TEM photographs for comparison, andFIGS. 32(d), 32(e) and 32(f) are traced drawings of FIGS. 32(a), 32(b)and 32(c), respectively;

[0110]FIG. 33 is a graph illustrating the TDDB life;

[0111]FIG. 34 is a schematic view illustrating one example of the wholeconstitution of a CMP apparatus used for a manufacturing method of asemiconductor integrated circuit device according to Embodiment 2 of thepresent invention;

[0112]FIG. 35 is a schematic view illustrating a part of a CMP apparatusused for the formation of a Cu-embedded interconnection;

[0113]FIG. 36 is a schematic view of a CMP apparatus illustrating thepolished condition of a Cu film;

[0114]FIG. 37 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating the manufacturing method of a semiconductorintegrated circuit device according to Embodiment 2;

[0115]FIG. 38(a) is a fragmentary plan view of the semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to Embodiment 2 and FIG. 38(b) is afragmentary cross-sectional view of the substrate;

[0116]FIG. 39 is a fragmentary cross-sectional view of the semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to Embodiment 2;

[0117]FIG. 40(a) is a fragmentary plan view of the semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to Embodiment 2 and FIG. 40(b) is afragmentary cross-sectional view of this substrate;

[0118]FIG. 41 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to Embodiment 2;

[0119]FIG. 42(a) is a fragmentary plan view of the semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to Embodiment 2 and FIG. 42(b) is afragmentary cross-sectional view of this substrate;

[0120]FIG. 43 is a flow chart showing the manufacturing method of thesemiconductor integrated circuit device according to Embodiment 2;

[0121]FIG. 44 is a graph illustrating TDDB;

[0122]FIG. 45 is a flow chart showing a manufacturing method of asemiconductor integrated circuit device according to Embodiment 3;

[0123]FIG. 46 is a graph illustrating TDDB;

[0124]FIG. 47 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing method of a semiconductorintegrated circuit device according to Embodiment 4;

[0125]FIG. 48(a) is a fragmentary plan view of a semiconductor substrateillustrating the manufacturing method of the semiconductor integratedcircuit device according to Embodiment 4 and FIG. 48(b) is a fragmentarycross-sectional view of this substrate;

[0126]FIG. 49 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to Embodiment 4;

[0127]FIG. 50 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing method of a semiconductorintegrated circuit device according to another Embodiment;

[0128]FIG. 51 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to another Embodiment;

[0129]FIG. 52(a) is a fragmentary plan view of a semiconductor substrateillustrating the manufacturing method of the semiconductor integratedcircuit device according to another embodiment and FIG. 52(b) is afragmentary cross-sectional view of this substrate;

[0130]FIG. 53 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to another Embodiment;

[0131]FIG. 54 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating the manufacturing method of the semiconductorintegrated circuit device according to another Embodiment;

[0132]FIG. 55 is a graph showing measured data of TDDB characteristicsof copper, aluminum and tungsten interconnections;

[0133] FIGS. 56(a) to 56(c) illustrate a sample used in the presentapplication for the measurement of TDDB, wherein FIG. 56(a) is a planview, and FIGS. 56(b) and 56(c) are cross-sections taken along linesB-B′ and C-C′ of FIG. 56(a), respectively;

[0134]FIG. 57 is a schematic view illustrating the summary of themeasurement; and

[0135]FIG. 58 illustrates one example of measuring results of currentand voltage.

DETAILED DESCRIPTION OF THE INVENTION

[0136] The general meaning of each of the terms used in this applicationwill next be described.

[0137] The term “TDDB” as used herein means time (lifetime) determinedby applying a relatively high voltage between electrodes under measuringconditions of a predetermined temperature (ex. 140° C.), drawing a graphwherein time from application of voltage to dielectric breakdown isplotted against applied electric field, and extrapolating the practicalelectric field strength (ex. 0.2 MV/cm) in the graph. FIG. 56illustrates a sample used in the present application for the measurementof TDDB, wherein FIG. 56(a) is a plan view, and FIGS. 56(b) and 56(c)are cross-sections taken along lines B-B′ and C-C′ of FIG. 56(a),respectively. This sample can be formed practically in a TEG (TestEquipment Group) region of a wafer. As illustrated in FIG. 56, a pair ofcomb-like interconnections L are formed in the second interconnectionlayer M2 and are connected with pats P1, P2 of the uppermost layer. Anelectric current is measured by applying an electric field between thesecomb-like interconnections L. The pads 1, 2 are measuring terminals. Thewidth, distance between any two adjacent interconnections and thicknessof the comb-like interconnections L are each 0.5 μm. The length of theinterconnection is formed to 1.58×10⁵ μm. FIG. 57 is a schematic viewillustrating the summary of measurement. The sample is supported on ameasuring stage S and a current-voltage measuring apparatus (I/Vmeasuring apparatus) is connected between the pads P1 and P2. The samplestage S is heated by a heater H to adjust the temperature of the sampleto 140° C. FIG. 58 shows one example of the measuring results ofcurrent-voltage under the conditions of the sample temperature of 140°C. and electric field strength of 5 MV/cm. Although TDDB is measured byeither one of the constant voltage stress method and low current stressmethod, the former one wherein an average electric field applied to aninsulating film shows a fixed value is employed in the presentapplication. After application of voltage, the current density decreaseswith the passage of time and then, a drastic increase in the current(dielectric breakdown) is observed. Here, the time until the leakcurrent density reaches 1 μA/cm² is designated as TDDB (the TDDB at 5MV/cm). The term “TDDB” as used herein means the breakdown time(lifetime) at 0.2 MV/cm unless otherwise specifically referred to, butin a broader sense, it is sometimes used as a time until breakdown at apreliminarily designated electric field strength. Unless otherwisespecifically described, the TDDB means that at the sample temperature of140° C. The TDDB is measured using the above-described comb-likeinterconnections L, but it is needless to say that it reflects thebreakdown lifetime between actual interconnections.

[0138] The term “plasma treatment” as used herein means treatment ofexposing the surface of a substrate or, when a member such as insulatingfilm or metal film is formed on the substrate, the surface of the memberto the circumstance under plasma condition and giving chemical ormechanical (bombardment) action of the plasma to the surface. Plasma isusually formed by, while supplementing a specific gas (treating gas) asneeded in a reaction chamber substituted with the gas, ionizing the gasby the action of high-frequency electric field or the like. In practice,however, it is impossible to completely substitute the chamber with thetreating gas. In the present application, therefore, the term “ammoniaplasma” does not indicate complete ammonia plasma and existence ofimpurity gases (nitrogen, oxygen, carbon dioxide, water vapor and/or thelike) contained in the plasma is permitted. It is needless to say thatthe plasma may contain a diluting gas or additive gas.

[0139] The term “plasma of reducing atmosphere” as used herein means theplasma circumstance wherein reactive radicals, ions, atoms or moleculeshaving reducing action, that is, oxygen pulling action, predominantlyexist. Radicals and ions embrace atomic or molecular radicals and ions.In the plasma circumstance, not only single reactive one but also pluralreactive ones may be contained. For example, a hydrogen radical and NH₂radical may coexist in the circumstance.

[0140] The term “made of copper” as used herein means that copper isused as a main component. High-purity copper inevitably containsimpurities so that a member made of copper is permitted to containadditives or impurities. The term “made of high-purity copper” as usedherein means that copper is a high-purity material (ex. 4N (99.99%) andcontains any impurities of about 0.01%. This will apply to, not onlycopper, but also another metal (titanium nitride, or the like).

[0141] The term “gas concentration” as used herein means a flow rate ofa gas in the mass flow. Described specifically, when the concentrationof gas A in a mixture of gas A and gas B is 5%, it means Fa/(Fa+Fb)=0.05wherein Fa represents the mass flow rate of gas A and Fb represents themass flow rate of gas B.

[0142] The term “polishing liquid (slurry)” usually means a suspensionobtained by mixing abrasive grains in a chemical etching agent, but inthis application, it embraces a polishing liquid free of an abrasivegrain for the convenience sake of this invention.

[0143] The term “abrasive grains (slurry grains)” usually means powdersuch as alumina or silica contained in a slurry.

[0144] The term “chemical mechanical polishing (CMP)” usually meanspolishing of a surface to be polished by relatively moving a polishingpad, which is made of a relatively soft cloth-like sheet material, in asurface direction under the condition brought into contact with thepolishing pad, while supplying a slurry. This invention also embracesCML (Chemical Mechanical Lapping) wherein polishing is conducted bymoving a surface to be polished relative to the surface of a hardabrasive.

[0145] The term “abrasive-grain-free chemical mechanical polishing”means chemical mechanical polishing using a slurry having a weightconcentration of the abrasive grains less than 0.5%, while the term“abrasive-grain-using chemical mechanical polishing” means chemicalmechanical polishing using a slurry having a weight concentration of theabrasive grain not less than 0.5%. They are however relative naming. Inthe case where chemical mechanical polishing is conducted using abrasivegrains in each of the first and second steps, that in the first step issometimes called abrasive-grain-free chemical mechanical polishing ifthe polishing concentration of the first step is smaller by at least onefigure, desirably at least 2 figures, than that of the second step.

[0146] The term “anticorrosive” means a chemical for preventing orsuppressing the progress of polishing by CMP by forming an anticorrosiveand/or hydrophobic protecting film on the metal surface andbenzotriazole (BTA) is usually employed as the chemical (refer toJapanese Patent Application Laid-Open No. HEI 8-64594, for furtherdetails).

[0147] The term “conductive barrier layer” is usually a layer forpreventing atoms or ions, which constitute an embedded interconnectionmaterial, from being transported (including, being diffused) and therebyhaving an adverse effect on an underlying element and it means a layermade of a conductive material having a comparatively higher conductivitythan an insulating film and having diffusion-inhibiting properties, forexample, a metal such as Ti, a metal nitride such as TiN, a conductiveoxide or a conductive nitride.

[0148] The term “selective removal”, “selective polishing”, “selectiveetching” or “selective chemical mechanical polishing” means that havinga selection ratio of at least 5.

[0149] The term “embedded interconnection” usually means aninterconnection formed by an interconnection forming technique such assingle damascene or dual damascene, more specifically, by embedding aconductive film inside of a groove or the like, which has been formed inan insulating film, and then removing an unnecessary portion of theconductive film on the insulating film.

[0150] With regards to the selection ratio, when a selection ratio of “Ato B” (or “A relative to B”) is X, it means, if the case of polishingrate is taken, that the selection ratio becomes X according to thecalculation of a polishing rate of A based on that of B.

[0151] In the below-described embodiments, descriptions on the same orlike parts will essentially be omitted unless particularly necessary.

[0152] In the below-described embodiments, a description will be madeafter divided in plural sections or in plural embodiments if necessaryfor convenience's sake. These plural sections or embodiments are notindependent each other, but in a relation such that one is amodification example, details or complementary description of a part orwhole of the other one unless otherwise specifically indicated.

[0153] In the below-described examples, when a reference is made to thenumber of elements (including the number, value, amount and range), thenumber of elements is not limited to a specific number but can be notgreater than or less than the specific number unless otherwisespecifically indicated or in the case it is principally apparent thatthe number is limited to the specific number. Moreover in thebelow-described embodiments, it is needless to say that the constitutingelements (including element steps) are not always essential unlessotherwise specifically indicated or in the case where it is principallyapparent that they are essential.

[0154] Similarly, in the below-described embodiments, when a referenceis made to the shape or positional relationship of the constitutingelements, that substantially analogous or similar to it is alsoembraced. This also applies to the above-described value and range.

[0155] The term “semiconductor integrated circuit device” as used hereinmeans not only that formed over a single crystal silicon substrate butalso that formed over an SOI (silicon on insulator) substrate, asubstrate for the production of TFT (Thin Film Transistor) liquidcrystals or the like unless otherwise specifically indicated. The term“wafer” means a single crystal silicon substrate (substantiallydisk-shape in general), SOS substrate, glass substrate, anotherinsulating, semi-insulating or semiconductor substrate or a compositesubstrate thereof, which is employed for the fabrication of asemiconductor integrated circuit device.

[0156] The embodiments of the present invention will next be describedspecifically based on the accompanying drawings. In all the drawings fordescribing the embodiments, like members of a function will beidentified by like reference numerals and overlapping descriptions willbe omitted.

[0157] (Embodiment 1)

[0158] A manufacturing method of COM-LSI according to Embodiment 1of thepresent invention will next be described in the order of steps based onFIGS. 1 to 19.

[0159] As illustrated in FIG. 1, after formation of an element isolatinggroove 2 of about 350 nm deep is formed, by photolithography and dryetching, in a semiconductor substrate (which will hereinafter be called“substrate”) 1 having a specific resistance of about 1 to 10 Ωcm andbeing made of p-type single crystal silicon, a silicon oxide film 3 isdeposited, by CVD, over the substrate 1 including the inside of thegroove. The surface of the silicon oxide film 3 over the groove is thenflattened by chemical mechanical polishing (CMP), followed by ionimplantation of p-type impurities (boron) and n-type impurities(phosphorus) to the substrate 1, whereby a p-type well 4 and an n-typewell 5 are formed. Then, by steam oxidation of the substrate 1, a gateoxide film 6 of about 6 nm thick is formed over the surface of each ofthe p-type well 4 and n-type well 5.

[0160] As illustrated in FIG. 2, a gate electrode 7 having alow-resistance polycrystalline silicon film, WN (tungsten nitride) filmand W (tungsten) film is formed over the gate oxide film 6. Thepolycrystalline silicon film can be formed by CVD, while the WN and Wfilms can be formed by sputtering. The gate electrode 7 is formed bypatterning of these deposited films. The gate electrode 7 may be formedby the laminate film of a low-resistance polycrystalline silicon filmand W silicide film. After the formation of the gate electrode, n− typesemiconductor region 11 of a low impurity concentration and a p-typesemiconductor region 12 of a low impurity concentration are formed inthe p-type well 4 and n-type well 5, respectively, by ion implantation.

[0161] As illustrated in FIG. 3, a side wall spacer 13 is then formed onthe side wall of the gate electrode 7, for example, by depositing asilicon nitride film by CVD and anisotropic etching of the film. Ionimplantation is thereafter conducted, whereby n⁺ type semiconductorregion 14 (source, drain) having a high impurity concentration and p⁺type semiconductor region 15 (source and drain) having a high impurityconcentration are formed in the p-type well 4 and n-type well 5,respectively. Examples of the n-type impurities include phosphorus andarsenic, while those of the p-type impurities include boron. Then, ametal film such as titanium or cobalt is deposited, followed by heattreatment. By the so-called silicide method to deposit a metal film suchas titanium or cobalt and after heat treatment, remove the unreactedmetal film, a silicide layer 9 is formed on the surface of each of then⁺ type semiconductor region 14 (source, drain) and p⁺ typesemiconductor region 15 (source, drain). By the steps so far mentioned,an n-channel type MISFETQn and p-channel type MISFETQp are completed.

[0162] As illustrated in FIG. 4, a silicon oxide film 18 is depositedover the substrate 1 by CVD, followed by dry etching of the siliconoxide film 18 with a photoresist film as a mask, whereby a contact hole20 and a contact hole 21 are formed over the n⁺ type semiconductorregion 14 (source, drain) and p⁺ type semiconductor region 15 (source,drain), respectively. At the same time, a contact hole 22 is also formedover the gate electrode 7.

[0163] The silicon oxide film 18 is formed from a film having highreflow properties capable of embedding a narrow space between gateelectrodes 7,7, for example, BPSG (Boron-doped Phospho Silicate Glass)film. Alternatively, an SOG (Spin On Glass) film formed by spin coatingcan be used.

[0164] Then, a plug 23 is formed inside of each of the contact holes 20,21 and 22, for example, by depositing a TiN film and a W film by CVDover the silicon oxide film 18 including the inside of each of thecontact holes 20, 21 and 22, and removing the unnecessary portion ofeach of the TiN film and W film over the silicon oxide film 18 bychemical mechanical polishing (CMP) or etching back to leave these filmsonly inside of each of the contact holes 20, 21 and 22.

[0165] As illustrated in FIG. 5, W interconnections 24 to 30, which areto be a first interconnection layer, are formed over the silicon oxidefilm 18, for example, by depositing a W film over the silicon oxide film18 by sputtering, and dry etching this W film with a photoresist film asa mask. The W interconnections 24 to 30 of the first layer areelectrically connected with the source and drain (n⁺ type semiconductorregions) of the n-channel type MISFETQn, the source and drain (p⁺ typesemiconductor regions) of the p-channel type MISFETQp or the gateelectrode 7 through the contact holes 20, 21 and 22.

[0166] As illustrated in FIGS. 6(a) and 6(b), a silicon oxide film 31 isdeposited over the W interconnections 24 to 30 of the first layer. Afterthrough-holes 32 to 36 are formed in the silicon oxide film 31 by dryetching with a photoresist film as a mask, a plug 37 is formed inside ofthe through-holes 32 to 36.

[0167] The silicon oxide film 31 is deposited, for example, by CVD usingozone (or oxygen) and tetraethoxysilane (TEOS) as source gases. The plug37 is formed, for example, from a W film in a similar manner to thatemployed for the formation of the plug 23 inside of each of the contactholes 20, 21 and 22.

[0168] As illustrated in FIGS. 7(a) and 7(b), a thin silicon nitridefilm 38 of about 50 nm thick is deposited over the silicon oxide film 31by plasma CVD, followed by deposition of a silicon oxide film 39 ofabout 450 nm thick over the silicon nitride film 38 by plasma CVD. Thesilicon oxide film 39 and silicon nitride film 38 over the through-holes32 to 36 are removed by dry etching with a photoresist film as a mask,whereby interconnection grooves 40 to 44 are formed.

[0169] The interconnection grooves 40 to 44 are formed by selectivelyetching the silicon oxide film 39 using the silicon nitride film 38 asan etching stopper and then etching the silicon nitride film 38. It ispossible to control the depth of each of the interconnection grooves 40to 44 with good precision by forming, in advance, the thin siliconnitride film 38 below the silicon oxide film 39 in which theinterconnection grooves 40 to 44 are to be formed, stopping etching onceat the surface of the silicon nitride film 38 and then etching thesilicon nitride film 38.

[0170] The Cu-embedded interconnections to be a second interconnectionlayer are formed inside of the interconnection grooves 40 to 44 by thefollowing process.

[0171] As illustrated in FIG. 8, after deposition, by sputtering, of athin TiN (titanium nitride) film 45 of about 50 nm thick over thesilicon oxide film 39 including the insides of the interconnectiongrooves 40 to 44, a Cu film 46 sufficiently thicker (ex. about 800 nm)than the depth of each of the interconnection grooves 40 to 44 isdeposited over the TiN film 45 by sputtering. Then, the substrate 1 isheat treated in a non-oxidizing atmosphere (ex. hydrogen atmosphere) ofabout 475° C. to cause reflow of the Cu film 46, whereby the Cu film 46is fully embedded inside of each of the interconnection grooves 40 to44.

[0172] Here, the Cu film 46 is formed by sputtering and it is embeddedin the groove by reflow. Alternatively, a thin Cu film can be formed bysputtering, followed by the formation of another Cu film correspondingto the Cu film 46 by plating.

[0173] Owing to the diffusing tendency of Cu in the silicon oxide film,when the Cu interconnection is formed inside of each of theinterconnection grooves 40 to 44, Cu diffuses into the silicon oxidefilm 39, thereby causing a short-circuit between interconnections or anincrease in the parasitic capacitance between interconnections due to anincrease in the dielectric constant of the silicon oxide film 39. Inaddition, Cu is poor in adhesion to an insulating material such assilicon oxide so that it tends to cause peeling at the interface withthe silicon oxide film 39.

[0174] Accordingly, when a Cu interconnection is formed inside of eachof the interconnection grooves 40 to 44, it is necessary to dispose abarrier layer which can suppress diffusion of Cu between the siliconoxide film 39 and Cu film 46 and at the same time, has high adhesion toan insulating material. Furthermore, when the Cu film 46 is embeddedinside of each of the interconnection grooves 40 to 44 by thereflow-sputtering method as described above, the barrier layer isrequired to have properties to improve the wetness of the Cu film 46upon reflow.

[0175] High melting-point metal nitrides, such as TiN, WN and TaN(tantalum nitride), which hardly react with Cu are suited as such abarrier layer. It is also possible to use as the barrier layer ahigh-melting point metal nitride added with Si (silicon) or ahigh-melting-point metal such as Ta, Ti, W or TiW alloy which hardlyreacts with Cu.

[0176] The formation process of the Cu interconnection which will bedescribed below can be adapted to not only the formation of a Cuinterconnection with a high-purity Cu film but also to the formation ofa Cu interconnection with an alloy film having Cu as a main component.

[0177]FIG. 9 is a schematic view illustrating a single-wafer type CMPapparatus 100 to be used for the polishing of the Cu film 46. This CMPapparatus 100 is equipped with a loader 120 for accommodating therein aplurality of the substrates 1 each having the Cu film 46 formed on thesurface thereof, a polishing treatment part 130 for polishing andflattening the Cu film 46, a corrosion treatment part 140 for subjectingthe surface of the substrate 1 to corrosion treatment after completionof polishing, an immersion treatment part 150 for maintaining thesubstrate 1 to have a wet surface until the post washing of thesubstrate 1 after completion of the corrosion treatment, a post-washingtreatment part 160 for post-washing the substrate 1 after completion ofthe corrosion treatment and an unloader 170 for accommodating therein aplurality of substrates 1 after completion of post-washing.

[0178] The polishing treatment part 130 of the CMP apparatus 100 has, asillustrated in FIG. 10, a box-like body 101 which is opened at the topthereof. A rotating shaft 102 attached to this box-like body 101 has, atits upper end portion, a polishing disc (platen) 104 to be turned anddriven by a motor 103. This polishing disc 104 has, on the surfacethereof, a polishing pad 105 formed by uniformly bonding thereto aporous synthetic resin.

[0179] In addition, this polishing treatment part 130 is equipped with awafer carrier 106 for supporting the substrate 1. A driving shaft 107equipped with the wafer carrier 106 is turned and driven by a motor (notillustrated), integrated with the wafer carrier 106, and at the sametime, moved vertically above the polishing disc 104.

[0180] The substrate 1 is supported by the wafer carrier 106 by a vacuumadsorption mechanism (not illustrated) disposed in the wafer carrier106, with the main surface, that is, a surface to be polished, down. Thewafer carrier 106 has, at the lower end thereof, a concave portion 106 ain which the substrate 1 is to be accommodated. When the substrate 1 isplaced in this concave portion 106 a, the surface to be polished becomesthe substantially same level with or slightly protruded from the bottomsurface of the wafer carrier 106.

[0181] Above the polishing disc 104, a slurry feeding pipe 108 isdisposed for feeding a polishing slurry (S) between the surface of thepolishing pad 105 and the surface of the substrate 1 to be polished andby the polishing slurry (S) fed from the lower end of the pipe, thesurface of the substrate 1 is chemically and mechanically polished. Asthe polishing slurry (S), usable is that obtained by dispersing ordissolving main components, for example, abrasive grains such as aluminaand an oxidizing agent such as hydrogen peroxide or an aqueous solutionof ferric nitrate, in water.

[0182] This polishing treatment part 130 is equipped with a dresser 109,which is a tool for smoothening (dressing) the surface of the polishingpad 105. This dresser 109 is installed to the lower end of a drivingshaft 110 which moves vertically above the polishing disc 104 and isturned and driven by a motor (not illustrated).

[0183] After completion of the polishing, the surface of the substrate 1is subjected to corrosion treatment at the corrosion treatment part 140.The corrosion treatment part 140 has a similar structure to that of thepolishing treatment part 130. First, the main surface of the substrate 1is pressed against a polishing pad attached onto the surface of apolishing disc (platen) and a polishing slurry is mechanically removed.Then, a chemical liquid containing an anticorrosive such asbenzotriazole (BTA) is fed to the main surface of the substrate 1,whereby a hydrophobic protecting film is formed on the surface portionof the Cu interconnection formed on the main surface of the substrate 1.

[0184] Mechanical washing (pre-washing) of the polishing slurry isconducted, for example, as shown in FIG. 11. The both sides of thesubstrate 1 turned within a horizontal plane are sandwiched bycylindrical brushes 121A,121B made of a porous synthetic resin such asPVA (polyvinyl alcohol) and are washed simultaneously while turning thebrushes 121A,121B within a plane vertical to the surface of thesubstrate 1. Upon corrosion treatment after pre-washing, the oxidizingagent in the polishing slurry adhered to the main surface of thesubstrate 1 at the polishing treatment part 130 is removed sufficientlyby conducting pure water scrub washing, pure water ultrasonic washing,pure water running water washing or pure water spin washing as neededprior to or simultaneously with the corrosion treatment, whereby ahydrophobic protecting film is formed under the conditions substantiallyfree from the action of the oxidizing agent.

[0185] After completion of the corrosion treatment, the substrate 1 istemporarily stored in the immersion treatment part 150 in order toprevent the surface from being dried. The immersion treatment part 150serves for maintaining the surface of the substrate 1, which hasfinished corrosion treatment, to be wet until post-washing and it hassuch a structure that the predetermined number of the substrates 1 areimmersed and stored in an immersion tank (storage container) from whichpure water is overflowed. Corrosion of the Cu interconnections 28 to 30can be prevented more completely by supplying the immersion tank withpure water cooled to a temperature low enough to substantially terminatethe progress of electrochemical corrosion of the Cu interconnections 28to 30.

[0186] In order to prevent drying of the substrate 1, it is possible toadopt another method such as supply of pure water shower, insofar as thesurface of the substrate 1 is kept wet by the method.

[0187] The substrate 1 transferred to the post-washing treatment part160 is subjected to post-washing at once with the wet state of thesurface being maintained. In this part, scrub washing (or brush washing)of the surface of the substrate 1 is carried out while supplying theretoa weakly alkaline chemical liquid such as a washing liquid containingNH₄ 0H to neutralize the oxidizing agent and then, foreign particlesformed upon etching are removed by an aqueous solution of hydrofluoricacid fed onto the surface of the substrate 1. Prior to or simultaneouslywith the scrub washing, the surface of the substrate 1 can be subjectedto pure water scrub washing, pure water ultrasonic washing, running purewater washing or pure water spin washing or the opposite surface of thesubstrate 1 can be subjected to pure water scrub washing.

[0188] After completion of the post-washing treatment, the substrate 1is rinsed with pure water, spin-dried and accommodated in the unloader170. A plurality of the substrates 1 are transferred in one lot to thesubsequent step.

[0189] As illustrated in FIG. 12, it is possible to prevent the surfaceof the substrate 1 during storage from being exposed to an illuminationlight by forming the immersion treatment part (wafer storing part) 150,which serves to prevent surface drying of the substrate 1 aftercompletion of the corrosion treatment, to have a light shadingstructure. By this structure, generation of a short-circuit current dueto the photovoltaic effect can be prevented. The immersion treatmentpart 150 is formed to have a light shading structure by covering theimmersion tank (storage container) with a shade sheet or the like,thereby reducing the illuminance inside of the immersion tank (storagecontainer) to 500 lux or less, preferably 300 lux or less, morepreferably 100 lux or less.

[0190] As illustrated in FIG. 13, the substrate 1 may be carried intothe drying treatment part rightly after the polishing treatment, inother words, rightly before the initiation of the electrochemicalcorrosion due to the oxidizing agent in the polishing slurry left on thesurface of the substrate and the water content in the polishing slurrymay be removed by forced drying. The CMP apparatus 200 shown in FIG. 13is equipped with a loader 220 for accommodating a plurality ofsubstrates 1 each having a Cu-film-formed surface, a polishing treatmentpart 230 for polishing and flattening the Cu film, thereby forming aninterconnection, a drying treatment part 240 for drying the surface ofthe substrate 1 after completion of the polishing, a post-washing part250 for post-washing the substrate 1 and an unloader 260 foraccommodating therein a plurality of the substrates 1 after completionof the post-washing. According to the Cu interconnection forming processusing this CMP apparatus 200, the substrate 1 subjected to polishingtreatment in the polishing treatment part 230 is transferred to thedrying treatment part 240 rightly after the polishing treatment, inother words, rightly before the initiation of the electrochemicalcorrosion reaction due to the oxidizing agent in the polishing slurryleft on the surface and in the drying treatment part, the water contentin the polishing slurry is removed by forced drying. Then, the substrate1 under a dried condition is transferred into the post-washing treatmentpart 250 and after the post-washing treatment, it is rinsed with purewater, spin-dried and then accommodated in the unloader 260. In thiscase, the surface of the substrate 1 is kept drying during the time justafter the polishing treatment to the initiation of the post-washing sothat the initiation of the electrochemical corrosion is inhibited, whichmakes it possible to prevent the corrosion of the Cu interconnectioneffectively.

[0191] By such a CMP method, the Cu film 46 and TiN film 45 over thesilicon oxide film 39 are removed and as illustrated in FIG. 14, the Cuinterconnections 46 a to 46 e are formed inside of the interconnectiongrooves 40 to 44.

[0192] In the next place, the surface of each of the Cu interconnections46 a to 46 e and silicon oxide film 39 are subjected to plasmatreatment. FIGS. 15(a) and 15(b) are cross-sectional view and plan vieweach schematically illustrating the apparatus used for plasma treatment.

[0193] In this apparatus, two treatment chambers 302 a, 302 b andcassette interface 303 are attached to a load lock chamber 301. The loadlock chamber 301 has therein a robot 304 for transporting the substrate1. Between the load lock chamber 301 and treatment chambers 302 a,302 b,a gate valve 305 is disposed for maintaining a high vacuum condition inthe load lock chamber 301 during treatment.

[0194] The treatment chambers 302 a, 302 b each has, therein, asusceptor 306 for supporting the substrate 1, a baffle plate 307 foradjusting a gas flow, a supporting member 308 for supporting thesusceptor 306, a mesh-like electrode 309 disposed opposed to thesusceptor 306 and an insulating plate 310 disposed substantiallyopposite to the baffle plate 307. The insulating plate 310 serves tocontrol the formation of a parasitic discharge in an unnecessary regionother than the region between the susceptor 306 and electrode 309. Onthe reverse side of the susceptor 306, a lamp 312 is installed inside ofa reflection unit 311 and from the lamp 312, an infrared ray 313 isirradiated to the susceptor 306 and substrate 1 through a quartz window314, whereby the substrate 1 is heated. The substrate 1 is installed onthe susceptor 306 with the face up.

[0195] The chambers 302 a, 302 b can be evacuated to make their insideshighly vacuum and a treating gas and high-frequency electric power arefed from a gas port 315. The treating gas is fed to the vicinity of thesubstrate 1, passing through the mesh-like electrode 309. The treatinggas is discharged from a vacuum manifold 316. The pressure is controlledby adjusting the gas flow rate and discharging rate. The high-frequencyelectric power is applied to the electrode 309, whereby a plasma isgenerated between the susceptor 306 and electrode 309. Thehigh-frequency electric power having, for example, a frequency of 13.56MHz is employed.

[0196] In the treating chamber 302 a, ammonia plasma treatment whichwill be described below is carried out. In the treating chamber 302 b, acap film (silicon nitride film) which will be described later is formedby deposition. Since the treating chambers 302 a and 302 b are connectedvia the load lock chamber 301, the substrate 1 can be transported to thetreating chamber 302 b without causing vacuum break after ammonia plasmatreatment, which makes it possible to carry out ammonia plasma treatmentand formation of the cap film continuously.

[0197] The substrate 1 is then subjected to ammonia plasma treatment byusing the above-described plasma treating apparatus. From the cassetteinterface 303, the substrate 1 is carried in the load lock chamber 301by the robot 304. After evacuation of the load lock chamber 301 to asufficiently pressure-reduced condition, the substrate 1 is transferredinto the treating chamber 302 a by the robot 304. Then, the gate valve305 of the treating chamber 302 a is closed and the treating chamber 302a is evacuated to a sufficient vacuum degree, followed by theintroduction of an ammonia gas into the treating chamber 302 a tocontrol the pressure to a predetermined value. An electric field is thenapplied to the electrode 309 from the high-frequency electric source.The surface of the substrate 1 is subjected to plasma treatment asillustrated in FIG. 16. After a lapse of a predetermined time, thehigh-frequency electric field is terminated, whereby the plasma isstopped. After evacuation of the treating chamber 302 a, the gate valve305 is opened and the substrate 1 is transported into the load lockchamber 301 by the robot 304. Since the load lock chamber 301 ismaintained under a high vacuum condition, the surface of the substrate 1is not exposed to the atmosphere.

[0198] The substrate 1, for example, having a size of 8 inches can besubjected to plasma treatment under the conditions of a treatingpressure of 5.0 Torr, RF electric power of 600 W, substrate temperatureof 400° C. and ammonia flow rate of 200 sccm and treating time of 10seconds. The distance between any two adjacent electrodes is set at 600mils. It is needless to say that the plasma treatment conditions are notlimited to the above-described ones. According to the study of thepresent inventors, a reduction in the plasma damage can be attained by ahigher pressure and a reduction in the scatter of TDDB and an increasein TDDB can be attained by a higher substrate temperature. It has alsobeen found that hillocks tend to appear on the surface of Cu at a highersubstrate temperature, a lager RF electric power or a long treatingtime. In consideration of these findings and a difference in theconditions depending on the constitution of the apparatus, the plasmatreatment conditions can be set within a range of from 0.5 to 6 Torr fortreating pressure, 300 to 600 W for RF electric power, 350 to 450° C.for substrate temperature, 20 to 500 sccm for ammonia flow rate, 5 to180 seconds for treating time and 300 to 600 mils for a distance betweenelectrodes.

[0199] By the plasma treatment, as described above, on the surface ofeach of the Cu interconnections 46 a to 46 e and silicon oxide film 39,a thin nitride film of each of the underlying films can be formed overthe surface of each of the Cu interconnections 46 a to 46 e and siliconoxide film 39, whereby adhesion between the cap film (silicon nitridefilm) which will be described later, and each of the Cu interconnections46 a to 46 e and silicon oxide film 39 can be improved, leading to amarked improvement in the TDDB characteristics.

[0200] Such an improvement brought by the plasma treatment will bedescribed later in detail based on the analysis of the test results bythe present inventors.

[0201] The substrate 1 is then transported into the treating chamber 302b by the robot 304. After the gate valve 305 of the treating chamber 302b is closed and the treating chamber 302 b is evacuated to a sufficientvacuum degree, a mixed gas of silane (SiH₄), ammonia and nitrogen isintroduced into the treating chamber 302 b and the pressure of thechamber is adjusted and maintained at a predetermined pressure. Anelectric field is applied to the electrode 309 from the high-frequencyelectric source to generate a plasma, whereby the silicon nitride film47 (cap film) is deposited over the surface of each of the Cuinterconnections 46 a to 46 e and silicon oxide film 39 as illustratedin FIG. 17. After a lapse of a predetermined time, the high-frequencyelectric field is terminated, whereby the plasma is stopped. Thetreating chamber 302 b is evacuated, followed by opening of the gatevalve 305 and transportation of the substrate 1 into the load lockchamber 301 by the robot 304. The substrate 1 is then discharged intothe cassette interface 303 by using the robot 304.

[0202] The silicon nitride film 47 is formed to a film thickness of, forexample, 50 nm. Then, a silicon oxide film for the formation of a plugto connect the third interconnection layer with the secondinterconnection layer (Cu interconnections 46 a to 46 e ) and in asimilar manner to that described above, the Cu-embedded interconnectionof at least the third layer is formed. FIG. 18 is a whole flow chart ofthe formation process of the above-described Cu interconnections 46 a to46 e.

[0203]FIG. 19 illustrates one example of CMOS-LSI in which the formationof the interconnections of the first to the seventh layers has alreadybeen finished. The first interconnection layer (M1) is made of atungsten film, as described above. The second interconnection (M2) tothe fifth interconnection (M5) layers are formed in a similar manner tothat employed for the formation of the above-described Cuinterconnection. In each of the second (M2) and third interconnection(M3) layers, the width, distance between the adjacent twointerconnections and height are each formed to 0.5 μm. In each of thefourth interconnection (M4) and fifth interconnection (M5) layers, onthe other hand, the width, distance between adjacent twointerconnections and height (thickness) are each formed to 1 μm. Thesixth interconnection (M6) is formed to have three layers, that is,tungsten film, aluminum film and tungsten film, while the seventhinterconnection layer (M7) is constituted from an aluminum film. A bumpor the like is formed on the seventh interconnection layer (M7), but itis not illustrated.

[0204] The embodiment of the present invention brings about a largeimprovement in the TDDB characteristics. FIG. 20 is a graph illustratingthe TDDB of a TEG sample formed in the same layer with the secondinterconnection layer M2 (Cu interconnections 46 a to 46 e) of thisEmbodiment, in which Line A indicates the data of this embodiment. Atthe same time, the TDDB (Line Ref) free from ammonia plasma treatment isshown for comparison. From the drawing, it has been found that the TDDBaccording to this embodiment is by about 6 figures better than that forcomparison.

[0205]FIG. 21 illustrates the data (Line B) when the silicon oxide film39 used in this embodiment is replaced by a silicon nitride film whichis denser and firmer than the silicon oxide film. Replacement of theinsulating film from silicon oxide to silicon nitride does not bringabout any difference (Line Ref) unless it is subjected to ammonia plasmatreatment. The TDDB characteristics can be improved more than thoseaccording to this embodiment by the use of the silicon nitride film asthe insulating film, followed by ammonia plasma treatment. Theimprovement is however not so marked, indicating that the ammonia plasmatreatment rather than the replacement has a dominant influence. Itsuggests that not an insulating film itself but its interface is adominant factor which controls TDDB.

[0206] With a view to analyzing the improving mechanism of the TDDBbrought by ammonia plasma treatment, the present inventors have carriedout surface analysis of copper and silicon oxide film. The results ofanalysis will next be described.

[0207] FIGS. 22 to 24 are graphs each illustrating the results of XPSanalysis (X-ray Photo-electron Spectroscopy) on the surface of the Cuinterconnection, wherein (a) and (c) are results of spectral analysis ofCu2p and (b) and (d) are those of N1s.

[0208] FIGS. 22(a) and 22(b) each illustrates the analysis results ofthe as-deposited surface of the Cu film. Since the peak of Cu2p isobserved but the peak of N1s is on the noise level, it has been foundthat no nitrogen exists in the as-deposited Cu film. FIGS. 22(c) and22(d) are analysis results of the surface of the Cu interconnectionrightly after the Cu film was subjected to CMP, from which both of theCu2p peak and the N1s peak are observed. As described above, BTA iscontained in a slurry so that nitrogen in the BTA remaining on the Cusurface is presumed to be observed. FIGS. 23(a) and 23(b) are analysisresults of the surface of the Cu interconnection which has beensubjected to post-washing after CMP. No change is observed in the peakof Cu2p, while the peak of N1s lowers, which is considered to owe to theremoval of BTA by washing. FIGS. 23(c) and 23(d) are analysis results ofthe surface of the Cu interconnection after the Cu interconnection isallowed to stand for 24 hours in the atmosphere after post-washing. Thepeak of CuO can be observed with the peak of Cu2p. No change can beobserved from the peak of N1s after the Cu interconnection is allowed tostand. It has been found that the Cu interconnection is oxidized byallowing it to stand, whereby CuO is formed.

[0209] FIGS. 24(a) and 24(b) illustrate the analysis results of thesurface of the Cu interconnection which has been oxidized, followed byammonia plasma treatment. The peak of CuO almost disappears, while thepeak of N1s appears strongly, which is presumed to owe to the reductionof the Cu surface and removal of oxygen, and at the same time, nitridingof the Cu surface. For comparison, the surface of the oxidized Cuinterconnection subjected to hydrogen thermal treatment at 350° C. wasanalyzed. The results are shown in FIGS. 24(c) and 24(d). When FIG.24(c) is compared with FIG. 24(a) concerning the peak of Cu2p, hydrogenthermal treatment is more reducing, because FIG. 22(a) shows the Cuinterconnection in a more as-deposited state. Judging from that N1s peakis hardly observed, the Cu surface is only reduced by the hydrogenthermal treatment.

[0210] From the above-described results, it has been found that thesurface of each of the Cu interconnections 46 a to 46 e has been reducedand at the same time, a nitride film has been formed on the surface.This nitride layer is considered to serve to suppress formation ofcopper silicide by preventing the reaction between copper and silanecontained in the raw material gas upon deposition of the silicon nitridefilm after ammonia plasma treatment. Prevention of silicide formation ispresumed to suppress an increase in the interconnection resistance.

[0211]FIG. 25 is a graph illustrating the results of XPS analysis on thesilicon oxide film, while FIGS. 26 and 27 each illustrates the resultsof the mass spectrometric analysis (TDS-APIMS) of the silicon oxidefilm. The analysis was conducted on each of the silicon oxide film afterCMP and post-washing (Profile C), that subjected to hydrogen plasmatreatment after CMP and post-washing (Profile D), that subjected toammonia plasma treatment after CMP and post-washing (Profile E) and thatsubjected to nitrogen plasma treatment after CMP and post-washing(Profile F). A deviation toward the high energy direction of about 1 eVin Profile C is caused by the influence of charge up.

[0212] FIGS. 25(a) and 25(b) each illustrates the observation data ofSi2p spectrum, wherein FIG. 25(a) illustrates the analysis data of about10 nm depth and FIG. 25(b) illustrates the analysis data of about 2 nm.FIGS. 25(c), 25(d) and 25(e) illustrate the observation data of N1s, O1sand C1s spectra, respectively.

[0213] In FIG. 25(b), a broad peak is observed on the lower energy side(at 102 eV) of hydrogen plasma treatment (Profile D), which is presumedto owe to the formation of an Si—H bond on the surface of the siliconoxide film by the hydrogen plasma treatment.

[0214] In FIG. 25(a), peaks of the ammonia plasma treatment (Profile E)and nitrogen plasma treatment (Profile F) at 105 eV are broad on thelower energy side and are therefore asymmetrical. The peak at theasymmetrical part (103.5 eV) is presumed to result from an Si—O—N bond.The surface of the silicon oxide film is considered to be nitrided bythe ammonia plasma treatment and nitrogen plasma treatment. Thecomparison between FIGS. 25(a) and 25(b) suggests that the nitriding isstronger on the surface portion. The nitriding due to ammonia plasmatreatment and nitrogen plasma treatment can also be confirmed from FIG.25(c).

[0215] It is apparent from FIG. 25(e) that carbon can hardly be detectedin the hydrogen plasma treatment (Profile D), suggesting that organicmatters on the surface have been removed by hydrogen plasma treatment.The peak at 289 eV after CMP (Profile C) is presumed to result from aC—O bond. A slurry is considered to remain after CMP.

[0216]FIG. 25(f) shows the amount of N estimated from the ratio of theSi peak to N peak. Substantially equal nitriding is considered to beconducted in ammonia plasma treatment and nitrogen plasma treatment.

[0217] FIGS. 26(a), 26(b), 26(c) and 26(d) are graphs illustrating themeasurement results of the mass number 41 (Ar—H), mass number 27 (C₂H₃),mass number 57 (C₄H₉) and mass number 59 (C₃H₇O), respectively. FIGS.27(a), 27(b), 27(c) and 27(d) are graphs illustrating the measurementresults of the mass number 28 (Si, C₂H₄), mass number 44 (SiO, C₃H₆),mass number 29 (SiH, C₂H₅) and mass number 31 (SiH₃), respectively.

[0218] It has been revealed from FIG. 26(a) that there is almost nodifference in the hydrogen release amount by the plasma treatment, butthe release temperature of the hydrogen plasma treatment (Profile D) is520° C. which is lower than another case (560° C.).

[0219] FIGS. 26(a), 26(b) and 26(c) suggest the release of organicmatters in each process, while FIGS. 27(a) to 27(d) suggest theexistence of a peak which does not result from the release of organicmatters. The peaks of FIGS. 27(a) to 27(d) existing within a range offrom 300 to 400° C. are presumed to result from Si, SiO, SiH, SiH₃,respectively. According to the comparison among these drawings, releaseof SiO is observed in each of the hydrogen, ammonia and nitrogen plasmatreatments, but release of each of SiH and SiH₃ is hardly observed inthe ammonia plasma treatment. In other words, an Si—O—N bond is formedby the ammonia plasma treatment and release occurs easily at arelatively low energy. The energy necessary for release is the highestin the nitrogen plasma treatment, while it is almost the same in thehydrogen plasma treatment and ammonia plasma treatment.

[0220] The above-described results indicate that an Si—OH or Si—O— bondwhich will be a cause for the dangling bond on the surface of thesilicon oxide film is terminated as a weak Si—O—N bond by the ammoniaplasma treatment. Upon formation of a silicon nitride film after theammonia plasma treatment, the Si—O—N on the very surface is released andthe Si—O bond of the bulk and Si—N of the silicon nitride film form astrong bond, whereby a continuous interface is formed. This is presumedto be a mechanism for improving the adhesion at the interface. Withoutthe ammonia plasma treatment, on the other hand, the surface of thesilicon oxide film rich in an Si—OH bond and ammonia which is a rawmaterial gas of the silicon nitride film would undergo condensation,leading to the formation of a number of Si—O— bonds, thereby causing adangling bond. If a number of dangling bonds exist on the interfacebetween the silicon oxide film and silicon nitride film, a leak path isinevitably formed there, which will be a cause for leak current betweeninterconnections and, in turn, dielectric break.

[0221] Based on the above-mentioned analysis results, it is presumedthat by the ammonia plasma treatment, the surface of the oxidized Cuinterconnection can be reduced into a Cu single element, it becomeselectrically more stable than ionized Cu and moreover, the interfacebetween the silicon oxide film and silicon nitride film becomes firm andcontinuous, which brings about a reduction in leak current and markedimprovement in the TDDB characteristics.

[0222]FIG. 28 is a TEM photograph of the ammonia-plasma-treatedinterface between the interconnection layer and silicon nitride film(cap film) according to this embodiment, while FIG. 29 is a TEMphotograph of the ammonia-plasma-treatment-free interface. Existence ofa thin film on the interface (shown by an arrow) can be confirmed inFIG. 28. This thin film is presumed to be a nitride layer as describedabove. In FIG. 29, on the other hand, such a film cannot be confirmed.

[0223] In addition, resistance of the Cu interconnection can be reducedaccording to this embodiment. FIG. 30 illustrates the measuring resultsof the resistance of each of the Cu interconnections subjected tovarious treatments. The resistance without treatment (without plasmatreatment) or after ammonia plasma treatment is significantly lowcompared with that after another treatment (hydrogen plasma treatment,hydrogen annealing or nitrogen plasma treatment). FIGS. 31 and 32 areeach a TEM photograph of the interface between the Cu interconnectionand cap film (silicon nitride film) subjected to one of thesetreatments. Nothing particular can be observed from the interface freeof treatment or after ammonia plasma treatment (FIG. 31), while a coppersilicide (CuSi) layer has been formed on the interface subjected tohydrogen annealing or nitrogen plasma treatment (FIG. 32). This silicidelayer is presumed to cause an increase in the resistance. Such asilicide layer is formed by the reaction with a silane gas uponformation of the silicon nitride film. By the ammonia treatment,however, a markedly thin nitride film is formed on the Cu surface and itfunctions as a blocking layer against the silicide formation. It ispresumed that in the case of hydrogen annealing or the like, however,only the reduction of the copper surface causes exposure of the activeCu surface, thereby accelerating reaction with silicon, resulting in atendency to form a silicide layer. In the case of hydrogen plasmatreatment (FIGS. 32(c), 32(f)), something is formed on the interface. Itis not always the case so that the degree of silicide formation ispresumed to be small in the case of hydrogen plasma treatment. In FIGS.31 and 32, in addition to the TEM photographs (FIGS. 31(a) and 31(b),FIGS. 32(a) to 32(c)), corresponding traced drawings (FIGS. 31(c) and31(d), FIGS. 32(d) to 32(f)) are shown below the TEM photographs forreference.

[0224] Based on the above-described analysis results, the followingmodel can be indicated as a deteriorating mechanism of the TDDBcharacteristics. Without ammonia treatment of the present embodiment,copper oxide (CuO) is formed on the surface of the Cu interconnectionand upon formation of a cap film (silicon nitride film 47), coppersilicide is formed. Such copper oxide or copper silicide is ionizedeasier than pure copper. Ionized copper is drifted by an electric fieldbetween interconnections and diffused into the insulating film betweeninterconnections. The interface between the insulating film (siliconoxide film 39) having copper interconnections embedded therein and capfilm (silicon nitride film 47) is discontinuous due to many danglingbonds formed thereon and is therefore poor in adhesion when it is freefrom ammonia treatment of this embodiment. Such dangling bonds serve toaccelerate diffusion of copper ions so that copper ions are drifted anddiffused along the interface. In other words, a leak path is formed onthe interface between the interconnections. Owing to the leak action forlong hours and, in addition, thermal stress by electric current, anincrease of leak current passing through the leak path is accelerated,leading to breakdown (TDDB).

[0225] In this embodiment, on the other hand, owing to the ammoniatreatment on the surface of each of the Cu interconnections 46 a to 46 e, an oxide layer on the surface thereof is reduced and disappears, andinstead, a thin nitride layer is formed. Copper silicide is thereforenot formed upon formation of the silicon nitride film 47, which makes itpossible to prevent the formation of a substance becoming a main supplysource of copper ions, which will be a cause for leakage and dielectricbreakdown.

[0226] In this embodiment, the surface of the silicon oxide film 39 issubjected to ammonia treatment, which makes it possible to continuouslyconnect the silicon oxide film with the silicon nitride film 47, reducethe density of dangling bonds and suppress the formation of a leak path.In other words, the present embodiment makes it possible to form,between the silicon oxide film 39 and silicon nitride film 47, aninterface capable of suppressing the generation of copper ions whichwill be a cause for lowering of TDDB and suppressing the diffusion ofcopper, leading to an improvement in TDDB.

[0227] The above-described analysis suggests that TDDB can also beimproved by hydrogen plasma treatment. Described specifically, by thehydrogen plasma treatment, the Cu surface is reduced and a dangling bondsuch as Si—O— or Si—OH which will be a cause therefor is terminated asSi—H. Upon formation of the silicon nitride film, the Si—H having a weakbond surface is released and substituted by Si—N. As a result, acontinuous interface is formed between the silicon oxide film andsilicon nitride film. The interconnection resistance, however, increasesas described above. FIG. 33 is a graph illustrating the data of the TDDBafter hydrogen plasma treatment. For reference, Line Ref (withouttreatment) and Line A (ammonia plasma treatment) are shown. The graphclearly shows that the hydrogen plasma treatment (Line C) brings about amarked improvement in TDDB. Relaxation of the plasma damage is expectedin the hydrogen plasma treatment so that the use of a material, as a capfilm, which is replaceable for the silicon nitride film and at the sametime, does not form a reaction product with Cu is particularlyeffective. The nitrogen plasma treatment (Line D), on the contrary,lowers TDDB, which is presumed to occur owing to an increase in thedeposit of an organic matter by the nitrogen plasma treatment as isapparent from FIG. 26 or FIG. 27.

[0228] Moreover, this embodiment is effective for heightening the peelstrength of the interface, thereby increasing the margin because ofimproved adhesion between each of the Cu interconnections 46 a to 46 eand silicon oxide film 39, and the cap film 47.

[0229] Treatment is not limited to that with a single gas such asammonia or hydrogen but with a mixed gas plasma with an inactive gassuch as nitrogen, argon or helium. More specifically, a mixed gas ofammonia with hydrogen, nitrogen, argon or helium or that of hydrogenwith ammonia, nitrogen, argon or helium can be employed. In addition, amixed gas including three or more gases selected from theabove-described ones may be used. The amount of hydrogen, ammonia orhydrogen+ammonia must be at least 5% of the total flow rate (mass flowrate).

[0230] (Embodiment 2)

[0231] A manufacturing method of the CMOS-LSI according to Embodiment 2of the present invention will next be described in the order of stepsbased on FIGS. 34 to 43.

[0232] The process of this embodiment is similar to that of Embodiment 1in steps illustrated in FIG. 1 to FIG. 8. The steps after CMP will nextbe described.

[0233]FIG. 34 is a schematic view illustrating one example of the wholeconstitution of the CMP apparatus employed for the formation of aCu-embedded interconnection.

[0234] As illustrated in the drawing, the CMP apparatus 400 has apolishing treatment part 401 and a post-washing treatment part 402disposed downstream thereof. The polishing treatment part 401 isequipped with two fixed disks (first disk 403A, second disk 403B) forpolishing a wafer (substrate) 1; a clean station 404 for subjecting thepolished substrate 1 to preliminary washing and its surface to corrosiontreatment, and a rotary arm 405 for transferring the substrate 1 amongthe loader, the first disk 403A, second disk 403B, clean station 404 andunloader 407.

[0235] Downstream of the polishing treatment part 401, a post-washingpart 402 is disposed for scrub washing of the surface of the substrate 1which has finished preliminary washing. The post-washing part 402 isequipped with a loader 408, first washing part 409A, second washing part409B, spin drier 410 and unloader 411. The post-washing part 402 issurrounded by a shading wall 430 to prevent the surface of the substrate1 from being exposed to light during washing and its inside is dark withan illuminance of 180 lux, preferably 100 lux or less. This shading wallis disposed because, if the substrate 1 having a polishing liquidattached to the surface thereof is exposed to light under wet condition,a short-circuit current passes through the pn junction by thephotoelectromotive force of silicon, and Cu ions are dissociated fromthe surface of the Cu interconnection connected to the p side (+side) ofthe pn junction, which causes corrosion of the interconnection.

[0236] As illustrated in FIG. 35, the first disk 403A is turned anddriven within a horizontal plane by a driving mechanism 412 disposedbelow the disk. The first disk 403A has, on the upper surface thereof, apolishing pad 413 which has been formed by uniformly adhering asynthetic resin such as polyurethane having a number of pores. A wafercarrier 415 turned and driven vertically within a horizontal plane by adriving mechanism 414 is disposed above the first disk 403A. Thesubstrate 1 is supported by a wafer chuck 416 and retainer ring 417,each disposed at the lower end of the wafer carrier 415, with its mainsurface (a surface to be polished) down; and is pressed against thepolishing pad 413 under a predetermined load. Between the surface of thepolishing pad 413 and the surface of the substrate 1 to be polished, aslurry (polishing liquid) S is fed through a slurry feeding pipe 418,whereby the surface of the substrate 1 to be polished is chemically andmechanically polished. Above the first disk 403A, a dresser 420 turnedand driven vertically within a horizontal plane by a driving mechanism419 is disposed. The dresser 420 has, at the lower end thereof, a basehaving thereon electrodeposited diamond particles, by which the surfaceof the polishing pad 413 is periodically shaven in order to preventclogging with the abrasive grains. The constitution of the second disk403B is almost similar to that of the first disk 403A except that it hastwo slurry feeding pipes 418 a, 418 b.

[0237] For the formation of the Cu interconnection by theabove-described CMP apparatus 400, the substrate 1 accommodated in theloader 406 is transported to the polishing treatment part 401 by therotary arm 405, followed by chemical mechanical polishing(abrasive-grain-free chemical mechanical polishing) (CMP of the firststep) using an abrasive-grain-free slurry, as illustrated in FIG. 36, onthe first disk 403A to remove the Cu film 46 outside the interconnectiongrooves 40 to 44 (FIG. 37).

[0238] The term “abrasive-grain-free chemical mechanical polishing” asused herein means chemical mechanical polishing using a polishing liquid(slurry) containing abrasive grains made of powders such as alumina andsilica in an amount less than 0.5%. As the content of the abrasivegrains in the polishing liquid, an amount less than 0.1 wt. % ispreferred, with that less than 0.01 wt. % being more preferred.

[0239] The polishing liquid having a pH adjusted to a range belonging tothe corrosive range of Cu and moreover, having a composition adjusted sothat the polishing selection ratio of the Cu film 46 to the TiN film 45(barrier layer) will become not less than 5 is employed. As such apolishing liquid, a slurry containing both an oxidizing agent and anorganic acid can be exemplified. Examples of the oxidizing agent includehydrogen peroxide, ammonium hydroxide, ammonium nitrate and ammoniumchloride, while those of the organic acid include citric acid, malonicacid, fumaric acid, malic acid, adipic acid, benzoic acid, phthalicacid, tartaric acid, lactic acid and succinic acid. Among theabove-exemplified oxidizing agents, hydrogen peroxide is preferredbecause it is free of a metal component and is not a strong acid. Amongthe above-exemplified organic acids, citric acid is preferred, becauseit is ordinarily employed as a food additive and has therefore lowtoxicity, its waste liquid is not so harmful and has a high solubilityin water. Employed in this embodiment is a polishing liquid obtained,for example, by adding 5 vol. % of hydrogen peroxide and 0.03 wt. % ofcitric acid to pure water and adjusting the content of the abrasivegrains to less than 0.01 wt. %.

[0240] By the chemical mechanical polishing with the above-describedpolishing liquid, the Cu surface is oxidized by an oxidizing agent,whereby a thin oxide layer is formed on the surface. When a substancefor making the oxide water-soluble is fed, the oxide layer elutes as awater solution and the oxide layer becomes thin. Exposed to theoxidizing substance again, the thin portion of the oxide layer becomesthick. By the repetition of this reaction, chemical mechanical polishingproceeds. Chemical mechanical polishing using such anabrasive-grain-free polishing liquid is described in detail in JapanesePatent Application Hei 9-299937 and Japanese Patent Application Hei10-317233 filed by the inventors of this application.

[0241] Polishing is carried out, for example, under the followingconditions: a load of 250 g/cm², rotational frequency of wafer carrierof 30 rpm, rotational frequency of disk of 25 rpm and slurry flow rateof 150 cc/min. As a polishing pad, hard pad (IC1400) produced byRodel/U.S.A. is employed. The polishing is terminated when theunderlying TiN film 45 appears by the removal of the Cu film 46 anddetection of the end point is conducted by detecting the torque signalstrength of the disk or wafer carrier when the object to be polishedchanges from the Cu film 46 to the Tin film 45. It is also possible todetect the end point by forming a pore in the polishing pad andobserving a change of light reflection spectrum from the surface of thewafer or by observing an optical spectrum change of the slurry.

[0242] As illustrated in FIG. 37, the Cu film 46 outside theinterconnection grooves 40 to 44 are almost removed and the underlyingTiN film 45 appears by the above-described abrasive-grain-free chemicalmechanical polishing. As illustrated in enlarged views of FIGS. 38(a)and 38(b), however, the Cu film 46 not removed completely remains in therecess (shown by an arrow) of the TiN film 45 which has inevitably beenformed along the underlying step difference.

[0243] The TiN film 45 outside the interconnection grooves 40 to 44 andthe Cu film 46 which has partially remained thereover are removed bytransferring the substrate 1 from the first disk 403A to the second disk403B and subjecting it to chemical mechanical polishing(abrasive-grain-using chemical mechanical polishing) (CMP of the secondstep) using an abrasive-grain-containing polishing liquid (slurry). Theterm “abrasive-grain-using chemical mechanical polishing” as used hereinmeans chemical mechanical polishing with a polishing liquid containingabrasive grains made of powders such as alumina and silica in an amountnot less than 0.5 wt. %. In this embodiment, a polishing liquid obtainedby mixing 5 vol. % of hydrogen peroxide, 0.03 wt. % of citric acid and0.5 wt. % of abrasive grains with pure water is used, but it is notlimited thereto. This polishing liquid is fed to the polishing pad 413of the second disk 403B through the above-described slurry feeding pipe418 a.

[0244] In abrasive-grain-using chemical mechanical polishing, the Cufilm 46 which has partially remained over the TiN film 45 is removed,followed by the removal of the TiN film 45 outside the interconnectiongrooves 40 to 44. The polishing of the surface of the Cu film 46 insideof the interconnection grooves 40 to 44 is suppressed by polishing underthe conditions to give a polishing selection ratio of the Cu film 46 tothe TiN film (barrier layer) not greater than that for theabove-described abrasive-grain-free chemical mechanical polishing, forexample, not greater than 3.

[0245] The polishing is conducted using a polishing pad “IC1400”produced by Rodel Inc., for example, under the conditions of a load of120 g/cm², wafer rotational number of 30 rpm, disk rotational number of25 rpm and slurry flow rate of 150 cc/min. The amount corresponding tothe film thickness of the TiN film 45 is polished and the end point ofpolishing is controlled by the time calculated from the thickness andthe polishing rate of the TiN film 45.

[0246] As illustrated in FIG. 39, the TiN film 45 outside theinterconnection grooves 40 to 44 are substantially removed and theunderlying silicon oxide film 39 appears by the above-describedabrasive-grain-using chemical mechanical polishing. As illustrated inthe enlarged views of FIGS. 40(a) and (b), the TiN film 45 notcompletely removed by the above-described polishing remains in therecess (shown by an arrow) of the silicon oxide film 39 which hasinevitably been formed along the underlying step difference.

[0247] Then, selective chemical mechanical polishing (CMP of the thirdstep) is conducted for removing the TiN film 45 (barrier layer) whichhas partially remained on the silicon oxide film 39 outside theinterconnection grooves 40 to 44 while suppressing the polishing of theCu film 46 inside of the interconnection grooves 40 to 44 as much aspossible. This selective chemical mechanical polishing is conductedunder the condition to give a polishing selection ratio of the TiN film45 to the Cu film 46 not less than 5 and at the same time, to give apolishing rate ratio of the silicon oxide film 39 to the Cu film 46 notless than 1.

[0248] The above-described selective chemical mechanical polishing isconducted using a mixture of a polishing liquid, as used in theabove-described abrasive-grain-using chemical mechanical polishing,which contains at least 0.5 wt. % of abrasive grains; and ananticorrosive. The anticorrosive is a chemical for preventing orcontrolling the progress of polishing by forming an anticorrosiveprotective film on the surface of the Cu film 46. Examples include BTAderivatives such as benzotriazole (BTA) and BTA carboxylic acid, dodecylmercaptan, triazole and tolyl triazole. A particularly stable protectivefilm is formed by the use of BTA.

[0249] Sufficient effects are usually available by the addition of BTA,as an anticorrosive, in an amount of 0.001 to 1 wt. %, more preferably0.01 to 1 wt. %, still more preferably 0.1 to 1 wt. % (three stages),though depending on the kind of the slurry. In this embodiment, amixture of 0.1 wt. % of BTA, as an anticorrosive, with the polishingliquid employed in the abrasive-grain-using chemical mechanicalpolishing in the second step is used, but it is not limited thereto.Polyacrylic acid or polymethacrylic acid, ammonium salt thereof orethylenediamine tetraacetic acid (EDTA) may be added as needed in orderto prevent lowering in the polishing rate due to the addition of ananticorrosive. The chemical mechanical polishing using a slurrycontaining such an anticorrosive is described in detail in JapanesePatent Application No. Hei 10-209857, Japanese Patent Application No.Hei 9-299937 or Japanese Patent Application No. Hei 10-317233 filed bythe inventors of the present application.

[0250] This selective chemical mechanical polishing (CMP of the thirdstep) is conducted on the second disk 403B successively after completionof the above-described abrasive-grain-using chemical mechanicalpolishing (CMP of the second step). The polishing liquid added with ananticorrosive is fed to the surface of the polishing pad 413 through theabove-described slurry feeding pipe 418 b. The polishing is conducted,for example, under the conditions of a load of 120 g/cm², wafer carrierrotational frequency of 30 rpm, disk rotational frequency of 25 rpm andslurry flow rate of 190 cc/min.

[0251] As illustrated in FIG. 41 and FIGS. 42(a) and 42(b), theabove-described selective chemical mechanical polishing completelyremoves the TiN film 45 outside the interconnection grooves 40 to 44,whereby the Cu-embedded interconnections 46 a to 46 e are formed insideof the interconnection grooves 40 to 44.

[0252] On the surface of the substrate 1 having Cu-embeddedinterconnections 46 a to 46 e formed thereon, the slurry residuecontaining particles such as abrasive grains or metal particles such asCu oxide has been attached. In order to remove this slurry residue, thesubstrate 1 is washed with BTA-containing pure water in the cleanstation 404 as shown in FIG. 34. At this time, megasonic washing whereinhigh-frequency vibration of 800 kHz or greater is applied to the washingliquid to release the slurry residue from the surface of the substrate 1may be used in combination. Then, the substrate 1, which is maintainedunder a wet condition to prevent surface drying, is transported from thepolishing treatment part 401 to the post-washing part 402. In the firstwashing part 409A, the substrate 1 is subjected to scrub washing with awashing liquid containing 0.1 wt. % of NH₄ 0H, followed by scrub washingwith pure water in the second washing part 409B. As described above, thepost-washing part 402 is covered with a shading wall 430 to preventcorrosion of the Cu interconnections 46 a to 46 e due to exposure of thesurface of the substrate 1 to light during washing.

[0253] After completion of the scrub washing (post-washing), thesubstrate 1 is dried by a spin drier 410 and then transported to thesubsequent step.

[0254] The steps after the scrub washing are similar to those ofEmbodiment 1. FIG. 43 illustrates the whole flow chart of theabove-described formation process of the Cu interconnections 46 a to 46e.

[0255] According to this embodiment, the TDDB characteristics can beimproved more than that of Embodiment 1. FIG. 44 is a graph illustratingTDDB and that of this embodiment is shown by Line E. For reference, TDDB(Line Ref) without treatment and that (Line A) subjected toabrasive-grain-using chemical mechanical polishing (Embodiment 1) areshown together. The TDDB is improved, as shown in Line F, only by theabrasive-grain-free chemical mechanical polishing without ammonia plasmatreatment. Such an improvement in TDDB is presumed to occur becausedamage to the silicon oxide film can be reduced in the case of theabrasive-grain-free CMP. In the case of the abrasive-grain-using CMP, onthe other hand, the slurry contains abrasive grains (such as alumina)having a particle size (secondary particle size) of 2 to 3 μm. Theseabrasive grains make micro scratches and cause a damage to the surfaceof the silicon oxide film 39. The abrasive-grain-free slurry does notcontain abrasive grains or contains, if any, a very small amount of themso that the damage can be lessened to the minimum. The improvement inTDBB is presumed to be brought about because of the above-describedreasons.

[0256] The TDDB characteristics will be improved further (Line G) byusing acid treatment (HF treatment), which will be described later, incombination. The acid treatment is conducted by treating the substrate 1with an acidic aqueous solution (ex. an aqueous HF solution) after CMPand post-washing but prior to ammonia plasma treatment. By the removalof the damaged layer on the surface by this acid treatment, the adhesionof the interface and, in turn, the TDDB are presumed to be improved.

[0257] (Embodiment 3)

[0258]FIG. 45 is a general flow chart of the formation process of the Cuinterconnections 46 a to 46 e. As illustrated in this drawing, thisprocess is similar to that of Embodiment 1 except that a washing stepwith HF or citric acid is added.

[0259] For HF washing, brush scrub washing can be employed. It can beconducted under the conditions of an HF concentration of 0.5% andwashing time for 20 seconds.

[0260] Alternatively, citric acid washing can be employed instead of HFwashing. For the citric acid washing, brush scrub washing can beemployed and it can be conducted under the conditions of a citric acidconcentration of 5% and washing time for 45 seconds.

[0261] By the HF or citric acid washing, the surface layer damaged byCMP or the like can be removed, which improves the TDDB characteristics.FIG. 46 is a graph illustrating TDDB, wherein Line H shows the data ofcitric acid washing, while Line I shows the data of HF washing, eachaccording to this embodiment. For reference, the data without treatment(Line Ref) and that of Embodiment 1 (Line A) are shown on the samegraph. As apparent from Line J, the TDDB characteristics show animprovement only by the HF washing without ammonia plasma treatment,which is presumed to result from an improvement in the properties of theinterface by the removal of the damaged layer.

[0262] (Embodiment 4)

[0263] FIGS. 47 to 49 are a plan view and cross-sectional viewsillustrating a manufacturing method of a semiconductor integratedcircuit device according to Embodiment 4 of the present invention. InFIGS. 47 to 49, only an interconnection part is shown.

[0264] As illustrated in FIG. 47, an insulating film 502 for theformation of an interconnection is formed over another insulating film501 and a copper interconnection 503 is formed by embedding it in thisinsulating film 502. The process for forming the copper interconnection503 is similar to that of Embodiments 1 to 3.

[0265] Then, a silicon nitride film 504 and a silicon oxide film 505 ofa low dielectric constant are formed, followed by the formation of asilicon oxide film (TEOS oxide film) 506 by the plasma CVD by using TEOSas a raw material gas.

[0266] The silicon oxide film 505 of a low dielectric constant is madeof a silicon oxide insulating film having a specific dielectric constant(∈) not greater than 3.0, for example, coating type insulating film suchas an inorganic SOG film formed using hydrogen silsesquioxane as a rawmaterial or an organic SOG film formed using tetraalkoxy silane andalkyl alkoxy silane as raw materials, or a fluorocarbon polymer filmformed by the plasma CVD. Use of such a silicon oxide film having a lowdielectric constant makes it possible to reduce the parasiticcapacitance between interconnections, thereby avoiding the problem ofdelay between interconnections.

[0267] A connecting hole 507 is then opened as shown in FIG. 48(b)according to the pattern as shown in FIG. 48(a). Photolithography andetching are applied to the opening of the connecting hole 507. Thesilicon oxide film 505 of a low dielectric constant has a rough surfaceand contains many Si—OH bonds. Experience has revealed that the qualityof the film formed over such a silicon oxide film or the condition ofthe interface therebetween are poor and that formation of a barrier film(titanium nitride) which will be described in the subsequent step overthe silicon oxide film without any treatment leads to inferior TDDBcharacteristics. The exposed portion of the silicon oxide film 505inside of the connecting hole 507 is therefore subjected to ammoniaplasma treatment as described in Embodiment 1. Then, the Si—OH bonds onthe surface are modified and converted into the Si—O—N bonds asdescribed in Embodiment 1.

[0268] As illustrated in FIG. 49, a plug 508 made of titanium nitrideand tungsten is formed in the connecting hole 507. Upon deposition oftitanium nitride, an Si—O—N bond is released as in Embodiment 1, wherebythe interface between titanium nitride and the silicon oxide film 50 ofa low dielectric constant is improved and adhesion therebetween isheightened.

[0269] It is needless to say that such plasma treatment in theconnecting hole can be applied to an interconnection groove.

[0270] Instead of ammonia plasma treatment, hydrogen plasma treatment orplasma treatment with a mixed gas with nitrogen, argon or helium canalso be adopted.

[0271] In the ashing step for the removal of a photoresist film afteropening of the connecting hole 507, the surface of the interconnection503 at the bottom of the connecting hole 507 happens to be oxidized. InJapanese Patent Application Laid-Open No. Hei 11-16912, described is atechnique for removing such an oxide layer.

[0272] The silicon oxide film 505 of a low dielectric constant can bedefined as a silicon oxide film having a dielectric constant lower thanthat of a silicon oxide film (ex. TEOS oxide film) contained in theprotective film formed as a passivation film.

[0273] The inventions made by the present inventors have so far beendescribed specifically based on the embodiments of the invention. Itshould however be borne in mind that the present invention is notlimited by these embodiments but can be modified within an extent notdeparting from the scope of the invention.

[0274] The above-described process for the formation of Cu-embeddedinterconnections 46 a to 46 e can also be applied to a process forforming a Cu-embedded interconnection by the dual damascene process. Inthis case, after formation of the W interconnections 24 to 30 of thefirst layer, a silicon oxide film 31 of about 1200 nm thick, a siliconnitride film 38 as thin as about 50 nm and a silicon oxide film 39 ofabout 350 nm thick are successively deposited by the plasma CVD over theW interconnections 24 to 30 of the first layer, as illustrated in FIG.50.

[0275] As illustrated in FIG. 51, the silicon oxide film 39, siliconnitride film 38 and silicon oxide film 31 over the W interconnections24, 26, 27, 29, 30 of the first layer were removed successively by dryetching with a photoresist film as a mask. As illustrated in FIGS. 52(a)and 52(b), the silicon oxide film 39 is removed by dry etching withanother photoresist film as a mask and with the silicon nitride film 38as an etching stopper, whereby interconnection grooves 50 to 54 servingalso as through-holes are formed.

[0276] As illustrated in FIG. 53, after deposition of a TiN film 45 asthin as about 50 nm over the silicon oxide film 39 including the insideof each of the interconnection grooves 50 to 54, a Cu film 46sufficiently thicker than the depth of each of the interconnectiongrooves 50 is formed over the TiN film 45. The interconnection grooves50 to 54 which also serve as through-holes have a larger aspect ratiothan the above-described interconnection grooves 40 to 44, so that theTiN film 45 is deposited by the CVD. The Cu film 46 is deposited byrepeating sputtering at least twice. Instead of sputtering, CVD,electroplating or electroless plating method can be adopted. Theformation of the Cu film 46 by the plating method requires a step forforming a Cu seed layer below the interconnection grooves 50 to 54 bysputtering or the like.

[0277] As illustrated in FIG. 54, the Cu film 46 and TiN film 45 outsidethe interconnection grooves 50 to 54 are removed by the above-describedabrasive-grain-free chemical mechanical polishing, abrasive-grain-usingchemical mechanical polishing and selective chemical mechanicalpolishing, whereby the Cu-embedded interconnections 46 a to 46 e areformed inside of the interconnection grooves 50 to 54. The stepssubsequent thereto are similar to those employed for the formation ofthe Cu-embedded interconnections 46 a to 46 e by the single damascenemethod.

[0278] It is needless to say that Embodiments 1 to 4 can be appliedeither singly or in combination. For example, after abrasive-grain-freechemical mechanical polishing according to Embodiment 2, acid treatmentis conducted according to Embodiment 3, followed by plasma treatmentwith ammonia, hydrogen or another gas according to Embodiment 1.

[0279] In the above-described embodiments, the silicon nitride film 47is formed continuously after ammonia plasma treatment without vacuumbreak. Alternatively, the silicon nitride film 47 may be formed afterammonia plasma treatment and vacuum break. The present invention is moreeffective when the silicon nitride film is formed without vacuum break.A thin nitride layer is however formed by ammonia plasma treatment sothat vacuum break and exposure to the atmosphere do not disturb thecontrol of the formation of an oxide layer. It is therefore possible tobring about effects of this embodiment to some extent even if vacuumbreak is conducted.

[0280] Effects of the representative inventions, among the inventionsdisclosed by the present invention, will next be described briefly.

[0281] Dielectric breakdown resistance (reliability) of a copperinterconnection formed by the damascene method can be improved.

[0282] Peeling of the interconnection layer from the cap film can becontrolled.

[0283] An increase in the resistance of a copper interconnection when asilicon nitride film is employed as the cap film can be prevented.

What is claimed is:
 1. A manufacturing method of a semiconductorintegrated circuit device, comprising the steps of: (a) forming a firstinterconnection groove in a first interlayer insulating film over afirst main surface of a wafer; (b) forming a first barrier metal filmover the first interlayer insulating film both outside inside the firstinterconnection groove; (c) forming a first interconnection metal filmhaving copper as a main component over the first barrier metal film bothoutside inside the first interconnection groove so as to fill the firstinterconnection groove; (d) removing both the first interconnectionmetal film and the first barrier metal film outside the firstinterconnection groove by chemical mechanical polishing; and thereafter(e) performing ammonia plasma treatment to the first main surface so asto reduce and nitride upper surfaces of both the first interlayerinsulating film and a remaining portion the first interconnection metalfilm, thereby reducing potential leakage current; and (f) forming acopper diffusion barrier insulating film over the first main surface. 2.The method according to claim 1, wherein step (f) is performed by plasmaCVD.
 3. The method according to claim 2, wherein steps (e) and (f) areperformed without exposing the wafer to the atmosphere.